The present invention relates generally to memories, and more specifically, to soft defect error detection in memories.
Memories require testing to ensure proper functionality prior to shipping the product. For example, memories are tested for soft-defects. Soft defects generally refer to those defects which appear under certain conditions and do not appear under other conditions. For example, a soft defect may be one that only appears at a specific voltage, temperature, and time. These soft defects are therefore difficult to detect. One known method for detecting soft defects tests SRAM (static random access memory) cells by writing predetermined data to them and reading them after a waiting period. However, the waiting period must be relatively long in order to ensure that all abnormal memory cells are failed which results in longer testing times. Therefore, any test techniques which require long waiting periods for testing incurs higher test cost. Furthermore, the above method fails to capture all soft-defects. Therefore, a need exists for an improved soft-defect detection technique which reduces testing cost and improves testing time.